±10 Vout from 24 Vin at 100 mA
Reference Design
PRD1209
FEATURES
Small Size
Low Cost
DESCRIPTION
This application note describes a SEPIC-Cuk converter used to create a dual rail output from a single input
voltage. A SEPIC-Cuk converter uses a SEPIC and a Cuk converter both tied to the same switch node to create
the two separate output rails. In this design, two readily available coupled inductors are used, though a custom
three winding transformer would also work. This design utilizes a cascoded FET (Q1) on the switch node. This
technique allows the use of an inexpensive low voltage regulator chip (ADP1613) to control a higher voltage
converter. In addition it results in very low switching loss, that is offset somewhat by the conduction loss in the
cascoded FET.
Table 1.
Sepcifications
Spec
Units
Vout1
+10V
Volts
Vout2
-10V
Volts
Iout1
0.1
Amps
Iout2
0.1
Amps
Tamb
55
degC
Vinmin
24
Volts
Vinmax
24
Volts
Rev. 0
Reference designs are as supplied “as is” and without warranties of any kind, express, implied, or
statutory including, but not limited to, any implied warranty of merchantability or fitness for a
particular purpose. No license is granted by implication or otherwise under any patents or other
intellectual property by application or use of reference designs. Information furnished by Analog
Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may
result from its use. Analog Devices reserves the right to change devices or specifications at any
time without notice. Trademarks and registered trademarks are the property of their respective
owners. Reference designs are not authorized to be used in life support devices or systems.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2009 Analog Devices, Inc. All rights reserved.
Reference Design
PRD1209
TABLE OF CONTENTS
Features ......................................................................................................................................................................1
Description .................................................................................................................................................................1
Revision History .........................................................................................................................................................2
Schematic ...................................................................................................................................................................3
Bill of Materials..........................................................................................................................................................3
Graphs ........................................................................................................................................................................5
TABLE OF FIGURES
Figure 1.
Schematic ...............................................................................................................................................3
Figure 2.
Bode Plot (Full Load both channels) .....................................................................................................5
REVISION HISTORY
2/17/2010—Revision 1: Initial Version
Rev. 1 | Page 2 of 6
Reference Design
PRD1209
SCHEMATIC
Figure 1.
Schematic
BILL OF MATERIALS
Table 2.
Des
Bill of Materials
MFG
Component
Specs
Part Number
Pkg
Qty
Area
(mm²)
Height
(mm)
Cost*
ADP1613ARMZ
MSOP-8
1
14.7
1.1
0.700
U1
ADI
Integrated
Switching
Regulator
L1
Coilcraft
47uH, 2200mΩ,
0.38Apk
LPD4012-473
4mm x 4mm
x 1.2mm
1
16.1
1.2
0.600
L2
Coilcraft
47uH, 2200mΩ,
0.38Apk
LPD4012-473
4mm x 4mm
x 1.2mm
1
16.1
1.2
0.600
Q1
Vishay
31 mΩ, 3.1
Vth,60 V
Si4850EY
SO8
1
31
1.75
0.680
Rev. 1 | Page 3 of 6
Reference Design
Des
MFG
D1
PRD1209
Component
Specs
Part Number
Pkg
Qty
Area
(mm²)
Height
(mm)
Cost*
ON
Semi
2 A, 100 V
MBRS1100T3G
SMB
1
21.3
2.4
0.100
D2
ON
Semi
2 A, 100 V
MBRS1100T3G
SMB
1
21.3
2.4
0.100
Cout1
Taiyo
Yuden
1uF, 16V, 9mΩ
EMK107 BJ105KA-T
0603
1
1.3
0.8
0.007
Cout2
Taiyo
Yuden
1uF, 16V, 9mΩ
EMK107 BJ105KA-T
0603
1
1.3
0.8
0.007
Cin1
Murata
0.1uF, 100V,
40mΩ
GRM188R72A104
0603
1
1.3
0.8
0.031
C1
Murata
0.1uF, 100V,
40mΩ
GRM188R72A104
0603
1
1.3
0.8
0.031
C2
Murata
0.1uF, 100V,
40mΩ
GRM188R72A104
0603
1
1.3
0.8
0.031
Rc1
Vishay
5% tolerance
2.32 kOhms
0805
1
2.5
0.5
0.005
Cc1
Vishay
10% tolerance
22 nF
0805
1
2.5
0.5
0.010
Cc2
Vishay
10% tolerance
100 pF
0805
1
2.5
0.5
0.010
Rf1B
Vishay
80.6 kOhms
1% tolerance
0805
1
2.5
0.5
0.005
Rf2
Vishay
11.3 kOhms
1% tolerance
0805
1
2.5
0.5
0.005
Cv5
Murata
1uF,10V,X5R
GRM188R61A105K
0603
1
1.3
0.6
0.010
Css
Vishay
10% tolerance
10 nF
0805
1
2.5
0.5
0.010
Z2
Diodes
Inc.
5.1V, 500 mW
Zener
DDZ9690
SOD-123
1
2.5
1.1
0.026
Rb1
Vishay
95.3 kOhms
5% tolerance
0805
1
2.5
0.5
0.005
Rb2
Vishay
1.78 kOhms
5% tolerance
0805
1
2.5
0.5
0.005
Q2
On
Semi
40V,NPN,300mW
MMBT3904LT1G
SOT-23
1
7.4
1.11
0.020
Totals
22
158.2 max=4.6
Rev. 1 | Page 4 of 6
3.00
Reference Design
PRD1209
GRAPHS
Figure 2.
Bode Plot (Full Load both channels)
Rev. 1 | Page 5 of 6
Reference Design
PRD1209
NOTES
©2009 Analog Devices, Inc. All rights reserved.
Trademarks and registered trademarks are the
property of their respective owners. Error! Unknown document property name.
Rev. 1 | Page 6 of 6